This invention relates to an internal combustion engine and, in particular, to a motor vehicle engine.

Engine designers always view engine compactness as an important consideration. Compactness for any engine is a design consideration. It is undesirable for an engine to be bulkier or heavier and more space consuming than required to perform its particular duty in operating a motor vehicle whether a motor car, a three wheeler or a 2 wheeler including motorcycles and scooters, If bulk, space occupied and weight are excessive, a number of capital and operating cost consequences result. First, an engine must be contained within a protective compartment in the case of a motorcar.

Obviously to keep manufacturing and sales costs as low as possible, it is undesirable for the protective compartment to be too large. In the case of a two wheeler, such as a motorcycle, space constraints are caused by different design considerations.

Space constraints for engine packaging apply to various vehicle types whether 2 wheeler, 3 wheeler or 4 wheeler as follows.

Generally, any engine used in 3-wheeler, 4 wheeler or larger vehicles comprises a cylinder head, a cylinder block, a crankshaft, a crankcase structure; and transmission and differential components Typically, the crankcase structure comprises some key engine elements for example crankshaft and transmission elements like input shaft, output shaft and so on. Generally, car engines have separate housing arrangements for crankcase, transmission system and differential.

Alternatively, the crankcase structure comprises two split portions (commonly known as crankcase halves) which are assembled together once the transmission and engine elements are fitted in a desired position inside the crankcase structure. Further there are additional housing for accommodating differential etc which are mounted separately on the above mentioned crankcase structure.. Such separate housing structures occupy space and add to engine weight.

It has always been a challenge for engine designers to make this arrangement compact still giving required engine performance, compactness being considered with respect to length, width and height of the engine.

Packaging of an engine within a three or four wheel vehicle in desired position or location presents challenges, for example where the engine is to be rear mounted. A convenient location for the engine may be beneath a bench seat of the vehicle. Current engines, with appropriate performance characteristics, are not easy to 5 " accommodate in this location because of the significant height constraint bearing in mind the need to accommodate cylinder block, cylinder head, transmission system and differential.

In addition, as rear wall location of vehicles imposes a significant constraint, a horizontal orientation of the kind involved in the Honda engine (Honda's Japanese Patent Publication No. 2006054009) which has crankshaft, input shaft, drive shaft and differential axes generally laid out, almost "in line", in a horizontal orientation is likely to be unacceptable even if oil starvation due to insufficient gradeability is addressed. Yet such rear engine location would be highly desirable to reduce vehicle length.

Height constraints have been addressed using horizontal engine orientations in which cylinder head, cylinder block, transmission system and differential are laid out horizontally as in the Honda specification. Engines are also known in which the transmission system is located adjacent the cylinder block and cylinder head.

A significant challenge in small engine development is to reduce space required by the transmission system and differential arrangement within the engine. In US 4798254, a transmission system for an automobile multi-cylinder engine is located in a volume bounded by planes respectively passing through differential and crankshaft axes The differential and transmission are located side by side with the crankshaft.

This arrangement addresses engine dimensional constraints of height and length but does not address constraints with respect to width of the engine, being a multi-cylinder engine which has a cylinder block taking up width. Also, this engine being multi-cylinder, does not require a balancer which further demands increases in engine length or height. Further in US 4798254, clutch, alternator and fly wheel and starting systems arrangements are employed outside the crankcase structure which occupy considerable amount of space outside the crankcase structure. Such space consumption is a serious constraint on engine compactness.

Further, in US 4798254, the crank case structure accommodating the transmission and differential elements has multiple compartments or splits (as shown by numerals 6b and 12) which pose several design, assembly and serviceability constraints. For example the differential axis, cylinder head and cylinder block must lie in same plane. Assembly of transmission components within the crankcase structure is difficult. Also, cylinder block replacement undesirably requires crankcase structure to be replaced as the cylinder block is integrated with the crankcase.

It is the object of the present invention to provide a compact internal combustion engine for rear location in a vehicle that is more compact in sideways, vertical and horizontal dimensions than conventional engine designs.

A vehicle using the compact engine may also be made compact by reducing space requirements for accommodating the engine.

With this object in view the present invention provides, in one aspect, an internal combustion engine suitable for rear location in a vehicle having at least one pair of wheels and comprising a cylinder head; a cylinder block accommodating an engine cylinder having a cylinder axis; and an crankcase having integral structure for accommodating crankshaft, alternator, clutch, transmission system and differential and said crankcase having two split portions connected in a plane parallel to said cylinder axis; wherein said cylinder has a cylinder axis passing through the crankshaft is inclined at an acute angle to a horizontal plane and wherein said engine is mounted below a rear seat of the vehicle with engine and transmission components being located, and preferably confined, substantially below the rear seat structure.

The vehicle is typically a three or four wheel vehicle. In a three wheel vehicle, the pair of wheels may be located at front or aft of the vehicle. In a four wheel vehicle, two pairs of wheels, front and rear would typically be provided.

Conveniently, the rear location of the engine is below the rear seat which has same height above the vehicle floor as in a comparable vehicle not having engine mounted below the rear seat. No seat re-design is required. The engine design therefore avoids the need for increasing seat height, vehicle height and cost resulting from the additional materials needed to build the vehicle. Engine and transmission (conveniently gear transmission) components are located, and preferably confined, substantially below the rear seat structure. Passenger safety is more assured if no part of the engine or transmission extends beyond the rear seat structure.

At the same time, rear seat and front seat height for passengers are at the same level above the floor in a vehicle using the engine.

Conveniently, the cylinder axis inclines from the horizontal plane toward the rear of the vehicle, preferably inclining upward toward a rear wall of a vehicle in which the engine is mounted. This facilitates maintenance of the engine since access to the cylinder head, for example through a panel in a rear wall of the vehicle, is easier from the rear of the vehicle. Such arrangement is also consistent with -v..maintaining a ground clearance for the engine whilst leaving space available as luggage space or space for other vehicle components, for example a vehicle battery.

The cylinder axis should be inclined to a horizontal plane passing through the crankshaft axis at as small an acute angle as possible, and ideally approaching as close to horizontal as engine operability considerations will allow, since this angle of inclination is a measure of engine compactness, the object of the present invention. That is, as the angle of inclination of cylinder to defining plane increases, the height of the engine also increases and compactness is lost.

The angle of inclination is therefore preferably between 10 and 20 degrees to the horizontal plane. This angle of inclination ensures efficient lubrication at the intended gradeability performance and well accommodates the height constraint required in mounting the engine below the rear seat and luggage space floor of a vehicle in which the engine is mounted.

The actual minimum angle of inclination as well as the optimal angle of inclination will depend on criteria which usefully include required gradeability, engine capacity and gear ratios. This angle of inclination ensures efficient lubrication at the intended gradeability performance and well accommodates the height constraint required in mounting the engine in vehicle.

The engine is advantageously a single cylinder engine, the single engine cylinder being selected to accommodate a side ways or width dimension constraint. Generally, a single cylinder engine will take up significantly less space than a multi-cylinder engine and is preferred even though balancing arrangements may be required to minimize engine vibrations.

The engine includes an air intake manifold and, where carbureted, the carburetor is connected to the engine through the air intake manifold The intake manifold desirably extends substantially parallel to cylinder head axis with its end portion curved in the transverse direction.

The carburetor is connected to the intake manifold end portion and lies within the transverse width of the engine and substantially below the bottom of luggage space floor assisting in compacting the overall engine structure. Further this arrangement assists safety of carburetor in case of any hitting of vehicle from rear side.

The engine may be carbureted or fuel injected. If the engine employs a fuel injection system, manifold injection is preferred rather than throttle body injection to maintain compactness with respect to height. The structure of the intake manifold conveniently remains substantially the same whether the engine is carbureted or fuel injected.
The engine must be packaged above the ground clearance to prevent damage to the engine from impact with road or drive way surfaces.

The engine may be mounted so as not to extend below vehicle floor and an extreme rear end of rear seat of the vehicle.

The engine may have a cooling system conveniently including a radiator; and radiator fan to enable convective air cooling of engine cooling water. In a conventional vehicle, the radiator would be mounted across the longitudinal axis of the vehicle. However, this requires greater vehicle length than if the radiator is oriented towards a side of the vehicle or along the longitudinal axis of vehicle, conveniently on a side cover of the engine extending in the direction of a longitudinal axis of the vehicle rather than transversely. The radiator fan is advantageously driven by the crankshaft, either directly or through a coupling.

The coupling could be of type where the fan can be connected/ disconnected as required from the crankshaft, for example by using electromagnetic clutch. An electrically operated radiator fan could be employed. Such side radiator mounting location well accommodates side ways dimensional constraint for engine mounting below the rear seat.
The engine comprises an exhaust system which typically includes a silencer. Rather than being chassis mounted, the silencer or muffler may conveniently be mounted directly on the crankcase, thus avoiding increase in engine length that would be required with a conventional muffler mounting location.

Chassis mounting brackets are not required with reduction in fitment stress on the silencer. At the same time, the orientation of the muffler is selected to reduce exhaust system tail pipe length and space consumption.

The engine typically includes a catalytic converter. This catalytic converter may be mounted relative to the muffler of the exhaust system to reduce exhaust system tail pipe length. In one preferred engine orientation, the catalytic converter would be mounted on the muffler. However, alternative arrangements are possible. For example, the catalytic converter could be located within the muffler body to minimize radiant heat transfer to the engine compartment.

In a conventional 3 or 4 wheeled vehicle, the alternator would be packaged separately, typically being belt driven. However, this could lead to breach of height - and length constraints on the rear mounted engine. The alternator is integrated with the crankshaft and driven directly without use of any belt. . The alternator's magnetic rotor is mounted on the crankshaft and the alternator stator (or coils) is mounted onto the crankcase and the whole arrangement may advantageously be run in presence of lubricating oil. A dry magneto could be used though this would require additional clearances and separating walls which increases engine size.

The two split portions of the crankcase structure are commonly known as halves. The crankshaft is conveniently journalled in the two portions with a suitable bearing arrangement such as a bush /journal or roller bearing arrangement. The crankcase is having integral structure for accommodating crankshaft, alternator, clutch, transmission system and differential and may advantageously comprise two sections defined by a vertical plane containing crankshaft axis, intersects said crankcase structure wherein a first section of the crankcase structure includes the cylinder block and differential, said first section also including the crankcase housing portion for accommodating the differential located proximate said cylinder block and cylinder head; and said second section of the crankcase structure accommodates a transmission system and a balancer for driving at least one engine component accommodated in the crankcase.

In this multi-section crankcase structure, the differential is conveniently be located proximate the cylinder head and cylinder block to assist engine compactness.. That does not require that the crankcase housing portion, housing the differential, contacts the cylinder head.

Crankshaft drive is transmitted to a vehicle drive shaft through the transmission system, conveniently a gear transmission system, which includes input shaft and output shaft and differential, input shaft and output shaft being mounted with gears corresponding with transmission ratios for the engine. Typically, between 3 and 5 transmission ratios would be provided. A 5 transmission ratio engine is particularly advantageous and can be achieved within the compact engine objective of the present invention.

The transmission system may include a drum shift type gear shift arrangement with a plurality of forward gears (located within the crankcase) and a reverse gear, this gear being located outside the drum length. Had it been necessary to locate the reverse gear within the span of drum length a larger drum length would be required which would necessitate larger crankcase volume, this reducing engine compactness. The gear shift mechanism is a drum shifter in which forks for reverse gear are formed integral with, rather than separate from, a shifter rail to save space and increase gear shift efficiency, by up to 30%. Movement of shifter rail enables movement of the fork and gear change in a drum shift gearbox. The integral fork mechanism may be employed suitably to any of the forward gears.

Conveniently, a centre point of crankshaft, input shaft and out put shaft are located substantially in the above mentioned plane along the crankshaft axis.

The engine conveniently includes water and/or oil pumps respectively provided for supplying water for water cooling of the cylinder head and crankcase; and lubricating oil for lubricating crankshaft, transmission and differential. Such pumps are driven from the crankshaft through a balancer linking crankshaft and drive shaft for water and oil pumps. Conveniently, such balancer, as well as water and/or oil pump(s), are located on the cylinder axis in the second section of the integral crankcase.

In such case, water and oil pump shafts are also located in the second or opposite section of the crankcase. Water and oil pumps may be driven by one common drive shaft linked with crankshaft through the balancer assisting the objective of engine compactness. Such common drive shaft is located in the opposite section.

The engine lubrication system is designed so as not to present challenges of oil starvation when a vehicle using the engine as prime mover negotiates upward and downward slopes. In addition, the engine - employing an integral crankcase -permits use of common oil for engine, transmission and differential. However, the engine requires an oil drainage path enabling oil to return to engine oil sump.

The above engine configuration provides flexibility in location of key engine and transmission components and provides optimum and balanced positioning of transmission and engine components, particularly in a single cylinder engine which could otherwise be subject to significant vibration.

In addition, the cylinder head and cylinder block are not formed integral with the crankcase but are rather connected to it at a mating surface. This makes engine serviceability easier. Further, the differential housing is positioned substantially in the centre of the engine and does not exceed the engine width. Additionally, the differential is desirably positioned substantially at the centre of wheel track, this arrangement allows use of drive shafts of identical and equal length. This reduces inventory cost as well wear and tear pattern is equal for both shafts. References to vertical plane (B-B) and horizontal plane (A-A) in the description and figures does not require that the engine is physically split at these planes.

The references to planes are used solely to aid visualisation of the engine. The engine is suitable for a number of motor vehicle applications where engine compactness is a particularly important objective. In this regard, the engine can be seen to have a compact configuration in all key dimensions, vertical, transverse and longitudinal.

In other words, the engine has the smallest possible bounded volume within these dimensions. The engine configuration allows ready mounting at the rear of the vehicle, most advantageously beneath the rear seat of a vehicle, especially a three or four wheel vehicle. This enables most efficient use of vehicle space and allows a compact vehicle with a compact engine to be produced.

The internal combustion engine of the present invention may be more fully understood from the following description of a preferred embodiment made with reference to the following drawings in which:

Fig. 1 is a left side schematic view of a vehicle including an internal combustion engine in accordance with one embodiment of the present invention.

Fig. 2 is a second left side schematic view of the vehicle of Fig. 1.

Fig. 3 is a right side schematic view of the internal combustion engine shown in Figs. 1 and 2.

Fig. 4 is a schematic top view of the internal combustion engine shown in Figs. 1 to 3.

Fig. 5 is a second right side schematic view of the internal combustion engine shown in Figs. 1 to 4.

Fig. 6 is a magneto side schematic view of the internal combustion engine shown in Figs. 1 to 5.

Fig. 7 is a schematic rear view of the internal combustion engine shown in Figs. 1 to 6.

Fig. 8 is a third left side schematic view of the internal combustion engine shown in Figs. 1 to 7.

Fig. 9 is a schematic top view of the internal combustion engine shown in Figs. 1 to 8.

Fig. 10 is a schematic view of the gear shift mechanism for the internal combustion engine of Figs, 1 to 9.

Figure 11 is a schematic rear view of the internal combustion engine of Figs. 1 to 8 showing differential and drive shaft.

Fig. 12a and 12b are schematic views of the internal combustion engine of Figs. 1 to 8 showing an oil drainage, oil return pathway and oil separation arrangement.

Fig. 13 is a right side schematic view of the internal combustion engine in accordance
with another embodiment of the present invention.

Fig. 14 is a right side schematic view of the internal combustion engine similar to that shown in Fig. 3 but provided with a fuel injection system.

Fig. 15 is a schematic rear view of the internal combustion engine shown in Fig. 14

Fig. 16 is a schematic partial rear view of the vehicle shown in Fig. 1.

Figures 1 to 9 show an internal combustion engine 100 of four stroke type to be mounted beneath the rear seat 510 of a four wheel vehicle 500. The rear seat 510, of bench style, is at conventional height above the vehicle floor 506 and at the same height above vehicle floor 506 as front seats 508. There are therefore constraints on the horizontal, vertical and transverse dimensions of the engine 100 in vehicle 510 as conveniently shown in Figs. 1 and 2 especially noting the need to accommodate rear luggage space 515. The horizontal or length constraint is imposed to prevent interference of engine 100 with rear wall 540 of vehicle 500. The vertical or height constraint is imposed to ensure accommodation of engine 100 beneath rear seat 510 but substantially at the height of vehicle floor 520 and ground clearance line 530 to prevent damage of the engine due to impact with a road or drive way surface.

Side ways or transverse dimension constraint is caused by different considerations in this three or four wheel vehicle application than in a contrasting motorcycle application where avoidance of interference with rider is an important consideration. In this case, it is important for space to be available to accommodate calf or heel of rear seated passengers. The passengers would ideally be seated on both sides of engine 100; and a fire wall or other shielding may be provided to protect the passengers from burns due to engine heat.

Engine 100 includes a cylinder head 119 and a cylinder block 117 accommodating a single cylinder 116 having a cylinder axis 200 and a crankcase 101. Crankcase 101 has two portions or halves 210 and 211 connected in a plane C-C parallel to cylinder axis 200 indicating the connecting or joining surfaces of the crankcase 101 halves in Figure 9. Crankshaft 120 is journalled between the two crankcase halves, which may be termed crankcase LHS and crankcase RHS, through a roller bearing arrangement.

Crankcase 101 has a mating surface 101A with cylinder block 117 and connection of the crankcase 101 and cylinder block 117 is at this mating surface 101A. Crankcase 101 and cylinder block 117 are not formed integral but are rather connected together. This assists engine servicing and cylinder block 117 replaceability, if required.

The cylinder block 117 and cylinder head 119 are both inclined at a same noticeably small acute angle, indeed substantially horizontal, to a transverse horizontal plane A-A intersecting crankcase 101 and an axis 122 of crankshaft 120. This small acute angle of inclination of cylinder block 117 and cylinder head 119, and cylinder axis 200, to horizontal plane A-A accords with the objectives of achieving engine and vehicle compactness, in particular by reducing engine height and facilitating location beneath the rear seat 510. The angle of inclination is 12.5 degrees to the horizontal plane A-A and compares with a gradeability of 11.8 degrees.

The 12.5 degrees angle was also selected taking engine capacity and gear ratios into account. Engine 100 as illustrated with reference to Figs. 1 to 13 and 16 is a carburetted engine and fuel and air are mixed in carburetor 114. The carburetor 114 is connected to engine 100 through air intake manifold 111A The intake manifold 111A extends along the cylinder head axis 200 with its end portion 111B curved in the transverse direction.

The carburetor 114 is connected to the said end portion 111B and lies within the transverse width of engine 100 and substantially below the bottom of luggage space 511 assisting in compacting the overall engine structure with respect to height and side ways and length dimensions. Further this arrangement assists safety of carburetor in case of any hitting of vehicle from rear side. Fuel/air mixture is then introduced to the engine 100 through air intake manifold 111A and intake valve 111.

Engine 100 may also be fuel injected and provided with a manifold injection system 250 as shown in Figs. 14 and 15 and similar to Fig. 3. Fuel injector 251 and throttle body 252 are mounted on the manifold 250. The engine 100 could alternatively be provided with a throttle body injection system but this would require more height and is therefore less desirable. Air is provided through intake manifold 111A which is essentially of the same design whether engine 100 is carbureted or fuel injected.

Whether engine 100 is carbureted or fuel injected, fuel is combusted in combustion chamber 110 of pent roof configuration and, during engine 100 operation, piston 115 is driven to reciprocate in cylinder 116 to cause rotation of crankshaft 120. As crankshaft 120 rotates it defines a volume of revolution 123. Crankshaft 120 includes a counter-balance 124, which reduces vibration. Crankshaft 120 is also integrated with an alternator 170. Crankshaft 120 drive is transmitted to a drive shaft of the engine 100 through a transmission system 141 and differential 146 housed within the integral housing portion 140 of crankcase 101. These components are located and confined beneath the rear seat 510. Exhaust gases from combustion are exhausted through exhaust valve 112 and exhaust passage 112A.

Cylinder head 119 is provided with an overhead valve train comprising intake and exhaust valves. Intake valve 111 and exhaust valve 112, two of which may be provided in a four valve single overhead cam engine, have timing controlled by a valve timing system comprising cams, operation of which is controlled by cam or timing chain 410 driven within a timing cavity 412 by sprocket 415. All these valve train components are lubricated with a lubricating oil supplied through the engine lubrication system.

Crankshaft 120, alternator 170, transmission system 141 and differential 146 and clutch 172 are all housed within the LHS and RHS portions 210 and 211 of crankcase 101; differential 146 as described above being housed within a differential housing portion 140 of crankcase 101. Crankcase 101 is therefore an integral crankcase as that term is understood in the engine arts, such crankcase 101 allowing use of common oil for engine 100, transmission system 141 and differential 146.

Crankcase 101 is divided into two sections 104 and 105 by a substantially vertical plane B-B intersecting the crankcase 101 containing the crankshaft axis 122. The two sections 104 and 105 include extensions 104a and 105a, having circular outer surfaces which form crankcase housing portion 140 housing the differential 146.

First section 104 includes the cylinder block 117, cylinder head 119 and differential 146, this being considered the cylinder section. The differential output shaft 147 is located in this cylinder section. Section 105, on the other side of plane B-B to section 104, is termed the second or opposite section and it accommodates key components of transmission system 141.

The differential 146 is located proximate the cylinder block 117 and cylinder head 119. The described engine arrangement makes the engine 100 compact in design in contrast to conventional designs where the differential 146 is distal from the cylinder block 117 and cylinder head 119 requiring greater engine height.

Transmission system 141 is a gear transmission system of drum shifter type, conventional for use in motorcycles, and includes output shaft 143, input shaft 142 and gear shifting drum 144. Crankshaft 120 and transmission system components such as input and output shafts 142 and 143 are substantially positioned in a plane perpendicular to the cylinder axis 200 which passes transversely through the centre of the crankshaft 120. The crankshaft 120 and transmission system components such as input and output shafts 142 and 143 are substantially positioned in a line perpendicular to the cylinder axis 200 which passes through the centre of the crankshaft 120. It follows that the crankshaft axis 122 is oriented perpendicular to the cylinder axis 200.

Each of input shaft and output shaft 142 and 143 are mounted with gears corresponding with transmission ratios for the engine. A 5 transmission ratio transmission system 141 with five forward gears is used in engine 100. A reverse idler gear 165 is also included within the transmission system 141. Centre points of crankshaft 120 and input shaft 142 are located substantially in the same plane, as vertical plane B-B, this facilitating engine 100 operability. Drive to the transmission system 141 is provided from crankshaft 120 through clutch 172.

Referring now to Figure 10, the fork arrangement 610 of the drum shift 144 is such that shifting rail 615 will move with gear shifting fork 617. That is, fork 617 is made integral with shifting rail 615.

Fork 617 and fork 619 are fixed on the shifting rail 615. Gear shifting drum 144 rotates about axis X-X during a gear shift. Due to provision of helical grooves 620 in the gear shifting drum 144 , fork 617 moves along the axis Y-Y and so shifting rail 615 and fork 619 also moves on the axis Y-Y. Sleeve 625, which is engaged with fork 619, also moves along axis Z-Z which results in the gear shifting of reverse gear 165. This avoids increase in length of the gear shifting drum 144 to accommodate reverse idler gear 165, thus making the gear shift arrangement compact and not demanding increase in the size of crankcase 101. The gear shift arrangement also achieves a 30 % improvement in gear shifting effort without any requirement to increase the length of gear shifting drum 144. This aids compactness, since forks 617 and 619 and shifting rail 615 are made integral and gear shifting efficiency.

Engine 100 includes a balancer 160 on the cylinder axis 200, the balancer being driven by crankshaft 120. Balancer 160 is located adjacent a crankcase 101 wall opposite to the cylinder block mating surface 101A at which integral crankcase 101 is connected to cylinder block 117, that is, in section 105.

The balancer 160 has been designed to reduce centre distance and to avoid interference with crankshaft 120 and counter balance 124. Engine 100 is water cooled and includes water and oil pumps 180 located within crankcase 101 as shown in Fig. 8. Such pumps are driven from the crankshaft 120 through the balancer 160 linking crankshaft 120 and drive shaft for water and oil pumps. Water and oil pumps 180 may be driven by one common drive shaft linked with crankshaft 120 through balancer 160. Such common drive shafts 551, 552 extend through section 104 of crankcase 101 opposite to the cylinder section 105. This further helps in achieving engine compactness.

Engine 100 includes a water cooling system including radiator 190 to enable convective air cooling of engine cooling water as conveniently shown in Figs. 4, 7 and 9. In a conventional vehicle, the radiator 190 would be mounted across the longitudinal axis of the vehicle. However, this requires greater vehicle length than if the radiator 190 is oriented towards the sides of the vehicle 500.

Radiator 190 is conveniently mounted on a side cover of the engine 100 extending in the direction of a longitudinal axis of the vehicle 500. This reduces side ways dimension which would be required with a conventional transverse radiator mounting. A radiator fan 195, to promote convective air cooling of water passing from cylinder head 119 through radiator hose 193 to the radiator 190, is located inboard of the radiator 190. The radiator fan 195 is directly driven by the crankshaft 120 as shown to avoid space requirement through provision of a belt drive.

Crankcase 101 may conveniently be used as a mounting member for mounting a range of engine components including starter motor 130 though the drive shaft of starter motor 130 is housed by an extension 102 of crankcase 101. This further assists in compactness.
Crankcase housing portion 140 housing the differential 146 forms a mounting member, for a muffler 300 forming part of the exhaust system 550 of the engine 100. In this case, muffler 300 - which includes a catalytic converter 320 for reducing emissions - is connected to crankcase housing portion 140 by a bracket 310.

This reduces space in comparison to a conventional exhaust system where the catalytic converter 320 would be located separate from the engine 100 increasing tail pipe length and taking up limited rear vehicle space in packaging it. Catalytic converter 320 is mounted on, and above, the muffler 300 to avoid increase in length of engine 100, and in particular exhaust tail pipe, length that would result in a conventional engine design. At the same time fitment stress is reduced over conventional engine design.

With reference to Figure 11, the differential 146 accommodated in differential housing portion 140 is positioned substantially in centre position of engine 100, thus accommodating the differential 146 within width of the engine 100 making the engine compact and symmetric in design. As shown in Fig, 16, the centre of differential 146 substantially matches with the centre 705 of wheel track 710 defining separation of rear wheels 700 of vehicle 500. This arrangement allows employment of identical and equal length of common drive shafts 551,552 which reduces inventory cost as well wear and tear pattern is equal for both the shaft.

Efficient lubrication of engine 100 is an important object and is simplified by use of a common oil to lubricate crankshaft 120, transmission system 141, differential 146 and timing chain 410. Efficient lubrication requires that oil be filtered and returned to the oil sump to prevent oil starvation.

Lubricating oil for engine 100 is filtered by oil filter 185, of conventional kind and circulated through engine 100, first being supplied to lubricate timing chain 410 and valve train components, such as the valve guides and cams of the valve timing system. Oil then flows through a drainage pathway of the engine lubricating system, as shown by arrow 'A' in Figs. 12a and 12b, in downward direction passing through passage/pocket 131 along an inclined surface defined by a downward sloping bottom wall 116 of the cylinder block 117 and cylinder head 119 towards the differential 146 through an opening 190 provided in the crank case wall 132.

The slope is of acceptable gradeability (here 12.5 degrees to horizontal) to ensure effective lubrication. The said pocket131 is offset down side of cylinder head sealing area 119a towards camshaft bearing wall 133 so as to prevent oil flowing beyond the sealing area 119a. The said bottom wall 116 is offset or lowered towards downside of sealing area 119a so that oil will not accumulate in the seal area and gets drained easily.

Oil coming from valve train components, such as timing or cam chain,is diverted by a separator plate 192 to be collected through an opening 191 in the crankcase wall behind clutch 172 and taken away from the clutch 172 towards oil sump as shown by arrows 'B'.

Separator ribs 173 located in crankcase 101 and clutch cover 134 restricts oil entering into the clutch 172 from the oil sump 175. Oil is recirculated through the oil drainage pathway by the oil pump 180.

The advantage of keeping oil away from clutch 172, and keeping a reduced dynamic oil level in this part of engine 100 by above mentioned arrangements, is reduced friction.

Oil coming from the cylinder head 119 is also collected through pocket 131 and inclined passage at bottom wall116 of head and block below head cover seal 119a level and diverted towards differential 146 shown by arrows 'A' through opening 190 in crankcase 101 wall. Such an oil drainage pathway avoids loading of the head cover seal 119a.The seal could be T seal or any other suitable sealing arrangement.

Inclusion of the oil drainage pathway within the engine design to recover oil to an oil sump 175, where it can be recirculated through engine 100 by oil pump 180, substantially avoids challenges of oil starvation when a vehicle using the engine 100 as the prime mover negotiates upward and downward slopes. In addition, the engine 100, employing an integral crankcase structure 101, permits faster warm up of the common oil for engine, transmission and differential. Still further, the engine design avoids integration of crankcase 101 and cylinder block 117. Such design enables easier engine servicing and replaceability of either crankcase or cylinder block 117, if required.

Modifications and variations to the internal combustion engine of the present disclosure may be apparent to skilled readers of this disclosure. Such modifications and variations are deemed within the scope of the present invention.

180 Oil Pump

185 Oil Filter

190 Radiator

191 Opening In The Crankcase Wall

192 Separator Plate

193 Radiator Hose

195 Radiator Fan

200 Cylinder Axis

210,211 Crankcase Halves

250 Fuel Injection system

251 Fuel injector

252 Throttle valve

300 Muffler

310 Bracket

320 Catalytic Converter

405 Timing Cavity

410 Cam Or Timing Chain

412 Timing Cavity

415 Sprocket

500 Four Wheel Vehicle

506 vehicle floor

506 front seats

510 Rear Seat

511 Luggage Space floor

515 Rear Luggage Space

520 Vehicle Floor

530 Ground Clearance Line

540 Rear Wall

550 Exhaust System

551,552 Drive Shafts

610 Fork Arrangement

615 Shifting Rail

617 Gear Shifting Fork

619 Fork

620 Helical Grooves

625 Sleeve

700 wheel

705 centre of wheel track

710 Wheel track

WE CLAIM:

1. An internal combustion engine suitable for rear location in a vehicle having at least one pair of wheels and comprising a cylinder head; a cylinder block accommodating an engine cylinder having a cylinder axis; and an crankcase having integral structure for accommodating crankshaft, alternator, clutch, transmission system and differential and said crankcase having two split portions connected in a plane parallel to said cylinder axis; wherein said cylinder has a cylinder axis passing through the crankshaft is inclined at an acute angle to a horizontal plane and wherein said engine is mounted below a rear seat of the vehicle with engine and transmission components being located, and preferably confined, substantially below the rear seat structure.

2. An engine as claimed in claim 1 wherein said cylinder axis inclines upwardly toward the rear of the vehicle.

3. An engine as claimed in claim 1 or 2 wherein said cylinder axis is inclined to said horizontal plane at as small an angle of inclination.

4. An engine as claimed in claim 3 wherein said angle of inclination is between 10 and 20 degrees to the horizontal plane.

5. An engine as claimed in any one of the preceding claims wherein said engine is mounted below said rear vehicle seat so as not to extend below a floor plane of a vehicle.

6. An engine as claimed in any one of claims 1 to 5 including an intake manifold extending substantially parallel to said cylinder head axis with an end portion of said inlet manifold being curved in a transverse direction of engine with a carburetor being connected to the intake manifold end portion such that said carburetor lies within the transverse width of the engine and substantially below the bottom of a vehicle luggage space when said engine is mounted in a vehicle.

7. An engine as claimed in any one of claims 1 to 5 including an intake manifold extending substantially parallel to said cylinder head axis with an end portion of said inlet manifold being curved in a transverse direction of engine with a fuel injection engine being connected to the intake manifold end portion such that said fuel injection system lies within the transverse width of the engine and substantially below the bottom of a vehicle luggage space when said engine is mounted in a vehicle

8. An engine as claimed in claim 7 wherein said fuel injection system is a manifold injection system.

9. An engine as claimed in any one of the preceding claims comprising an engine cooling system including a radiator and a radiator fan to enable convective air cooling of engine cooling water wherein said radiator is mounted on a side cover of the engine extending in the direction of a longitudinal axis of the vehicle.

10. An engine as claimed in any one of the preceding claims comprising an exhaust system wherein the muffler of said exhaust system is mounted directly on the crankcase.

11. An engine as claimed in claim 10 wherein said exhaust system includes a catalytic converter mounted above the muffler.

12. An engine as claimed in any one of the preceding claims wherein, when located in a vehicle, said differential is positioned substantially at the centre of a wheel track for said vehicle.

13. An engine claimed in claim 10 wherein said exhaust system includes a catalytic converter located within the muffler body.

14. A vehicle comprising the engine as claimed in any of the preceding one of claims.

15. A vehicle as claimed in claim 14 wherein said engine is mounted in a three or four wheel vehicle.

16. A vehicle as claimed in claim 15 wherein engine and transmission components are located, and preferably confined, below said rear seat structure.

17. A vehicle as claimed in claim 15 or 16 wherein said vehicle comprises front and rear seats, said rear seat and front seat are of same height and are being at the same level above a vehicle floor.